The goal of this clinical investigation is to determine whether first-degree relatives of patients with Crohn's disease have clinically silent intestinal inflammation. The central hypothesis of this study is that a proportion of first-degree relatives of patients with Crohn's disease manifest histologic and immunologic evidence of intestinal inflammation in the absence of clinical symptoms. This hypothesis will be tested by the following specific aims: Aim 1: Define the colonic and ileal endoscopic and histologic findings in asymptomatic first-degree relatives of Crohn's disease patients. Aim 2: Correlate the endoscopic and histologic findings in asymptomatic first-degree relatives of Crohn's disease patients with a functional analysis of intestinal integrity. Aim 3: Look for evidence of intestinal immune activation in asymptomatic first-degree relatives of Crohn's disease patients."